Nanocomposites containing layered nanoparticles and dispersant, composites, articles, and methods of making same

ABSTRACT

A nanocomposite is provided including layered nanoparticles and a dispersant dispersed in a curable resin, where the nanocomposite contains less than 2% by weight solvent. A composite is also provided including from about 1 to 70 weight percent of layered nanoparticles, and a dispersant, dispersed in a cured resin, and a filler embedded in the cured resin. Further, a method of preparing a nanoparticle-containing curable resin system is provided including mixing from 1 to 70 weight percent of aggregated layered nanoparticles with a curable resin and a dispersant to form a mixture. The mixture contains less than 2% by weight solvent. The method also includes milling the mixture in an immersion mill containing milling media to form a milled resin system including layered nanoparticles dispersed in the curable resin.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. application Ser. No. 14/911,110, filed Feb. 9, 2016, which is a national stage filing under 35 U.S.C. 371 of PCT/US2014/050663, filed Aug. 12, 2014, which claims priority to U.S. Application No. 61/865,308, filed Aug. 13, 2013; U.S. Application No. 61/909,575, filed Nov. 27, 2013; U.S. Application No. 61/918,302, filed Dec. 19, 2013; and U.S. Application No. 62/018,993, filed Jun. 30, 2014 the disclosures of which are incorporated by reference in their entirety herein.

TECHNICAL FIELD

The present disclosure relates to nanocomposites, composites, and articles that contain layered nanoparticles and dispersant, as well as methods of making the same.

BACKGROUND

A persistent issue for nanocomposites, and in turn composites that contain nanoparticles, is cost, including cost associated with the processing steps. One approach to processing nanocomposites is a solvent-based approach where an aqueous dispersion of nanoparticles is the raw material. The dispersion is typically dilute, in which the nanoparticles are present in an amount between about 15-40 weight percent. A solvent, typically a water-miscible solvent, is added in a 1:1 ratio with the water in the dispersion, further diluting the nanoparticles. The solvent is typically chosen so that the dispersed state of the nanoparticles is maintained. The solvent further serves to counteract the thickening effect of, for instance, silica nanoparticles, on resin systems. A surface treating agent is typically used to make the nanoparticles more compatible with the matrix resin. The surface treating agent is typically soluble in the water:solvent:nanoparticle dispersion. After completion of the surface treatment process, the modified nanoparticle dispersion is mixed with resin. This is followed by removal of the water and solvent to yield a nanocomposite.

There is a cost associated with the processes of preparing the nanoparticle aqueous dispersion, addition of solvent, surface treatment of the nanoparticles, compounding the nanoparticles into a resin, and removal of the water and solvent to form the nanocomposite. The removal of water and solvent is typically the most expensive of these processes.

Another approach to processing nanocomposites is the solvent-free approach where dry, aggregated particles are reduced in size, surface treated, and compounded into a resin by a mechanical grinding process (e.g., milling) without the aid of a solvent.

SUMMARY

The present disclosure provides nanocomposites and articles that contain layered nanoparticles, and methods of making the nanocomposites and articles, which have decreased cost of materials and processing, as compared to other preparation approaches.

In a first embodiment, the present disclosure provides a nanocomposite including layered nanoparticles and a dispersant, dispersed in a curable resin, wherein the nanocomposite contains less than 2% by weight solvent.

In a second embodiment, the present disclosure provides a composite including from about 1 to 70 weight percent of layered nanoparticles, and a dispersant, dispersed in a cured resin, and a filler embedded in the cured resin. The filler comprises at least one of a reinforcing continuous fiber, reinforcing discontinuous fibers, and hollow glass bubbles.

In a third embodiment, the present disclosure provides an article including from about 1 to about 70 weight percent of layered nanoparticles, and a dispersant, dispersed in a cured resin.

In a fourth embodiment, the present disclosure provides a method of preparing a nanoparticle-containing curable resin system including mixing from 1 to 70 weight percent of aggregated layered nanoparticles with a curable resin, a first dispersant, and optionally a catalyst, a diluent, a surface treatment agent, and/or a curing agent, to form a mixture. The mixture contains less than 2% by weight solvent. The method further includes milling the first mixture in a first immersion mill containing milling media to form a milled resin system comprising layered nanoparticles and the dispersant dispersed in the curable resin.

Various unexpected results and advantages are obtained in exemplary embodiments of the disclosure. One such advantage of exemplary embodiments of the present disclosure is the ability to produce low cost, high performance layered nanocomposites and articles. Another potential advantage of exemplary embodiments of the present disclosure is the ability to prepare dispersions of layered nanoparticles in curable resin and/or in a curing agent at high loading amounts without the use of solvents.

The above summary of the present disclosure is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The description that follows more particularly exemplifies illustrative embodiments. In several places throughout the application, guidance is provided through lists of examples, which examples can be used in various combinations. In each instance, the cited list serves only as a representative group and should not be interpreted as an exclusive list.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph presenting the measured viscosity of each of Comparative Example 1,

Comparative Example 2, Example 1, Example 2, and Example 3.

FIG. 2 is a graph presenting the measured storage modulus in the rubber plateau region and in the glassy region of each of Comparative Example 1a, Comparative Example 2a, Example 1a, Example 2a, and Example 3a.

FIG. 3A is a scanning electron microscope (SEM) image of Example 1a.

FIG. 3B is an SEM image of Example 1a, having a higher magnification than the SEM image of FIG. 3A.

FIG. 4A is a scanning electron microscope (SEM) image of Example 2a.

FIG. 4B is an SEM image of Example 2a, having a higher magnification than the SEM image of FIG. 4A.

FIG. 5A is a scanning electron microscope (SEM) image of Example 3a.

FIG. 5B is an SEM image of Example 3a, having a higher magnification than the SEM image of FIG. 5A.

DETAILED DESCRIPTION

Nanocomposites, composites, and articles are provided that contain layered nanoparticles, as well as methods of making the nanocomposites, composites, and articles. There is a need for a more efficient process for the incorporation of layered nanoparticles into nanocomposites and articles.

For the following Glossary of defined terms, these definitions shall be applied for the entire application, unless a different definition is provided in the claims or elsewhere in the specification.

Glossary

Certain terms are used throughout the description and the claims that, while for the most part are well known, may require some explanation. It should be understood that, as used herein:

As used in this specification and the appended embodiments, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. Thus, for example, reference to “a compound” includes a mixture of two or more compounds.

As used in this specification and the appended embodiments, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise. The term “and/or” means either or both. For example, the expression “A and/or B” means A, B, or a combination of A and B.

As used in this specification, the recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.8, 4, and 5).

Unless otherwise indicated, all numbers expressing quantities or ingredients, measurement of properties and so forth used in the specification and embodiments are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached listing of embodiments can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings of the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claimed embodiments, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

The term “comprises” and variations thereof do not have a limiting meaning where these terms appear in the description and claims.

The words “preferred” and “preferably” refer to embodiments of the disclosure that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the disclosure.

The term “nanoparticle” refers to particles that are submicron in size. The nanoparticles have an average particle size, which refers to the average longest dimension of the particles, that is no greater than 1000 nanometers, no greater than 500 nanometers, no greater than 200 nanometers, no greater than 100 nanometers, no greater than 75 nanometers, no greater than 50 nanometers, no greater than 40 nanometers, no greater than 25 nanometers, or no greater than 20 nanometers. The average particle size is often determined using transmission electron microscopy but various light scattering methods (e.g., laser diffraction) can be used as well. The average particle size typically refers to the average size of non-agglomerated and/or non-aggregated single nanoparticles.

The term “agglomerated” refers to a weak association of primary particles or aggregated particles usually held together by charge or polarity. Agglomerated particles can typically be broken down into smaller entities by, for example, shearing forces encountered during dispersion of the agglomerated particles in a liquid.

The terms “aggregated” and “aggregates” refer to a strong association of primary particles often bound together by, for example, residual chemical treatment, covalent chemical bonds, or ionic chemical bonds. Further breakdown of the aggregates into smaller entities is very difficult to achieve.

The term “spherical” means a round body whose surface is at all points equidistant from the center. The term “nonspherical” means any shape other than essentially spherical, including for example and without limitation, platelet, acicular, conical, diamond shaped, cubic, rhombohedral, pyramidal, and oval, and including regular and/or irregular shapes. For instance, a shape that is at least partially spherical but has portions missing from the sphere is encompassed by the term nonspherical.

The term “acicular” encompasses shapes such as rods, ellipsoids, needles, and the like. In certain embodiments, an acicular shape may further be hollow, e.g., a hollow needle shape. Certain nonspherical shapes have an aspect ratio of at least 2:1, at least 3:1, at least 5:1, or at least 10:1. The term “aspect ratio” refers to the ratio of the average longest dimension (e.g., of a nanoparticle) to the average shortest dimension.

As used herein, the term “silicate” refers to a compound including at least one SiO₂ or SiO₄ group and at least one metallic ion, and optionally including hydrogen. As used herein, the term “layered silicate” refers to a silicate having a structure that shears or cleaves into layers upon being subjected to mechanical force (and optionally treatment with an intercalating agent). The term “cationic clay” as used herein refers to a material containing silicon, aluminum, or magnesium, as well as oxygen and hydroxyl with various associated cations, and encompasses layered silicates.

As used herein, the term “layered double hydroxide” refers to a class of materials with positively charged layers and weakly bound charge-balancing anions located in the interlayer region, having a structure that shears or cleaves into layers upon being subjected to mechanical force (and optionally treatment with an intercalating agent). The term “anionic clay” as used herein refers to a material containing silicon, aluminum, or magnesium, as well as oxygen and hydroxyl with various associated anions, and encompasses layered double hydroxides.

As used herein, the term “intercalate” refers to insertion of a material between one or more layers of a layered nanoparticle. As used herein, the term “intercalated” refers to a layered nanoparticle containing at least two adjacent layers separated by a material that is disposed between the layers.

As used herein, the term “intercalating agent” refers to a material that is disposed between layers of layered nanoparticles to assist in intercalating and/or exfoliating layered nanoparticles.

As used herein, the term “exfoliate” refers to completely separating at least one layer of a layered nanoparticle from the one or more other layers of the layered nanoparticle. As used herein, the term “exfoliated” refers to a layered nanoparticle that has had at least one layer of a layered nanoparticle from the one or more other layers of the layered nanoparticle. A completely exfoliated layered nanoparticle has had all of its individual layers separated from each other.

As used herein, the term “silica” refers to amorphous silicon dioxide (SiO₂). As used herein, the term “pyrogenic” silica refers to silicon dioxide formed in flame or in sufficiently high temperature to decompose organic materials.

As used herein, the term “silica nanoparticle” refers to a nanoparticle having a silica surface. This includes nanoparticles that are substantially, entirely silica, as well nanoparticles comprising other inorganic (e.g., metal oxide) or organic cores having a silica surface. In some embodiments, the core comprises a metal oxide. Any known metal oxide may be used. Exemplary metal oxides include silica, titania, alumina, zirconia, vanadia, chromia, antimony oxide, tin oxide, zinc oxide, ceria, and mixtures thereof.

The term “curable” as used herein means chemically or physically crosslinkable to form a glassy, insoluble, non-flowable network which is maintained under normal use conditions.

The term “cured” as used herein means chemically or physically crosslinked in the form of a glassy, insoluble, non-flowable network which is maintained under normal use conditions.

The term “resin” as used herein means one polymer or at least two polymers blended together, in either solid or molten form.

The term “matrix” as used herein in the term “matrix resin” refers to a curable or cured resin into which additional components may be included (e.g., particles, fibers, etc.).

The term “nanocomposite” as used herein refers to a material comprising a curable or cured resin and nanoparticles.

The term “microcomposite” as used herein refers to a material comprising a curable or cured resin and microparticles, which is inclusive of microparticles and agglomerates and/or aggregates of nanoparticles.

The term “composite” as used herein refers to a cured nanocomposite comprising a cured resin, layered nanoparticles, and a filler comprising at least one of a continuous fiber, discontinuous fibers, and hollow glass bubbles. Continuous fibers include for example and without limitation, glass, carbon, basalt, ceramic (e.g., NEXTEL ceramic oxide fibers available from 3M Company (St. Paul, Minn.)), and organic fibers (e.g., aromatic polyamide (e.g., KEVLAR available from DuPont (Wilmington, Del.)), polypropylene, and polyacrylnitrile).

The term “article” as used herein refers to an object comprising a cured nanocomposite comprising a cured resin and layered nanoparticles, and optionally a filler comprising at least one of a reinforcing continuous fiber, reinforcing discontinuous fibers, and hollow glass bubbles (i.e., a composite).

The term “neat” as used herein in the term “neat resin” refers to a curable or cured resin which does not include a macroscopic filler (e.g., continuous or discontinuous fibers, hollow glass bubbles, etc.).

The term “(co)polymer” is inclusive of both homopolymers containing a single monomer and copolymers containing two or more different monomers.

The term “(meth)acrylic” or “(meth)acrylate” is inclusive of both acrylic and methacrylic (or acrylate and methacrylate).

The term “aliphatic group” means a saturated or unsaturated linear or branched hydrocarbon group. This term is used to encompass alkyl, alkenyl, and alkynyl groups, for example.

The term “alkyl group” means a saturated linear or branched hydrocarbon group including, for example, methyl, ethyl, isopropyl, t-butyl, heptyl, dodecyl, octadecyl, amyl, 2-ethylhexyl, and the like. The term “alkylene group” refers to a divalent alkyl group.

The term “heteroalkyl group” means an alkyl group having at least one —CH₂— replaced with a heteroatom such as O or S. In many embodiments, the heteroalkyl group is a monovalent polyether group. The term “heteroalkylene group” refers to a divalent heteroalkyl group. In many embodiments, the heteroalkylene group is a divalent polyether group.

The term “alicyclic group” means a cyclic hydrocarbon group having properties resembling those of aliphatic groups. The term “aromatic group” or “aryl group” means a mono- or polynuclear aromatic hydrocarbon group.

The term “unsaturation” means either a double bond between two atoms (e.g., C═C), or a triple bond between two atoms (e.g., C≡C).

When a group is present more than once in a formula described herein, each group is “independently” selected, whether specifically stated or not. For example, when more than one R group is present in a formula, each R group is independently selected.

The term “component” refers to any compound (e.g., any reactant), heterogeneous catalyst, solvent, or other material, which is present in a reactor.

Reference throughout this specification to “one embodiment,” “certain embodiments,” “one or more embodiments” or “an embodiment,” whether or not including the term “exemplary” preceding the term “embodiment,” means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the certain exemplary embodiments of the present disclosure. Thus, the appearances of the phrases such as “in one or more embodiments,” “in certain embodiments,” “in one embodiment,” “in many embodiments” or “in an embodiment” in various places throughout this specification are not necessarily referring to the same embodiment of the certain exemplary embodiments of the present disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments.

Various exemplary embodiments of the disclosure will now be described. Exemplary embodiments of the present disclosure may take on various modifications and alterations without departing from the spirit and scope of the disclosure. Accordingly, it is to be understood that the embodiments of the present disclosure are not to be limited to the following described exemplary embodiments, but are to be controlled by the limitations set forth in the claims and any equivalents thereof.

Thus, in a first exemplary embodiment, the disclosure provides a nanocomposite comprising layered nanoparticles and a dispersant, dispersed in a curable resin; wherein the nanocomposite comprises less than 2% by weight solvent. Preferably, the nanocomposite comprises less than 0.5% by weight solvent, or even more preferably the nanocomposite comprises essentially no solvent.

In a second exemplary embodiment, the disclosure provides a composite comprising from about 1 to 70 weight percent of layered nanoparticles, and a dispersant, dispersed in a cured resin, and a filler embedded in the cured resin. The filler comprises at least one of a reinforcing continuous fiber, reinforcing discontinuous fibers, and hollow glass bubbles. In certain embodiments, an article is provided comprising the composite.

In a third exemplary embodiment, the present disclosure provides an article comprising from about 1 to about 70 weight percent of layered nanoparticles, and a dispersant, dispersed in a cured resin.

In a fourth exemplary embodiment, the present disclosure provides a method of preparing a nanoparticle-containing curable resin system comprising mixing from 1 to 70 weight percent of aggregated layered nanoparticles with a curable resin, a first dispersant, and optionally a catalyst, a diluent, a surface treatment agent, and/or a curing agent, to form a mixture comprising less than 2% by weight solvent; and milling the first mixture in a first immersion mill containing milling media to form a milled resin system comprising layered nanoparticles and the dispersant dispersed in the curable resin.

Accordingly, in a third exemplary embodiment, an article is provided comprising a nanocomposite comprising from about 1 to about 70 weight percent of layered nanoparticles and a dispersant dispersed in a cured resin. In certain aspects, the article contains from about 1 to about 3 weight percent, or from about 10 to about 70 weight percent, or from about 1 to about 5 weight percent, or from about 15 to about 50 weight percent, or from about 20 to about 50 weight percent, or from about 25 to about 50 weight percent, or from about 15 to about 70 weight percent, or from about 25 to about 70 weight percent, or from about 35 to about 70 weight percent, or from about 50 to about 70 weight percent of the layered nanoparticles.

In certain embodiments, the nanocomposite or article further comprises one or more additional components (e.g., additives), for example and without limitation, catalysts, surface treatment agents, reactive diluents, curing agents, cure accelerators, defoamers, air release agents, crosslinking agents, dyes, flame retardants, pigments, impact modifiers, and flow control agents.

Layered nanoparticles often have an average width (smallest dimension) equal to at least 1 nanometer, at least 2 nanometers, or at least 5 nanometers. The average width of layered nanoparticles is often no greater than 250 nanometers, no greater than 100 nanometers, no greater than 50 nanometers, no greater than 25 nanometers, or no greater than 15 nanometers. The layered nanoparticles will have a different length than width, and can have an average length D1 measured by dynamic light scattering methods that is, for example, at least 25 nanometers, at least 50 nanometers, at least 75 nanometers, or at least 100 nanometers. The average length D1 (e.g., longer dimension) can be up to 200 nanometers, up to 400 nanometers, or up to 500 nanometers. Acicular layered particles may have an elongation ratio D1/D2 in a range of 5 to 30, wherein D2 means a diameter in nanometers calculated by the equation D2=2720/S and S means specific surface area in meters squared per gram (m²/gram) of the nanoparticle, as described in U.S. Pat. No. 5,221,497 (Watanabe et al.).

In certain embodiments, the layered nanoparticles are selected to have an average specific surface area equal to at least 20 m²/gram, at least 50 m²/gram, at least 100 m²/gram, at least 150 m²/gram, at least 200 m²/gram, at least 250 m²/gram, at least 300 m²/gram, or at least 400 m²/gram. Nanoparticles having average specific surface areas equal to at least 150 m²/gram often have an average diameter (e.g., longest dimension) less than 40 nanometers, less than 30 nanometers, less than 25 nanometers, or less than 20 nanometers.

Various sizes and/or various shapes of layered a nanoparticles may be used in combination. In certain embodiments, bimodal distributions of particle sizes may be used. For example, nanoparticles having an average particle size (i.e., of the length of the longest dimension) of at least 50 nanometers (e.g., in the range of 50 to 200 nanometers or in the range of 50 to 100 nanometers) can be used in combination with nanoparticles having an average particle size no greater than 40 nanometers. The weight ratio of the larger to smaller nanoparticles can be in the range of 2:98 to 98:2, in the range of 5:95 to 95:5, in the range of 10:90 to 90:10, or in the range of 20:80 to 80:20. Nanocomposites having a bimodal distribution of layered nanoparticles can include 2 to 20 weight percent layered nanoparticles having an average particle size of 40 nanometers or less and 2 to 40 weight percent layered nanoparticles having an average particle size of 50 nanometers or greater. The amount is based on a total weight of the nanocomposite. In an aspect, the layered nanoparticles comprise a bimodal particle size distribution. In another aspect, the layered nanoparticles comprise a unimodal particle size distribution. In some embodiments, the layered nanoparticle cores have a narrow particle size distribution.

The layered nanoparticles typically comprise an average particle size of the longest dimension in the range from about 1 nanometer to about 1000 nanometers, or from about 1 nanometer to about 500 nanometers, or from about 1 nanometer to about 100 nanometers, or from about 1 nanometer to about 50 nanometers, or from about 100 nanometers to about 400 nanometers, or from about 500 nanometers to about 1000 nanometers. In certain embodiments, the layered nanoparticles include a population of clusters of primary nanoparticles (e.g., an aggregate of layered nanoparticles), wherein the cluster is defined to have an irregular shape and is submicron in size. The population of clusters (i.e., the clusters within the population) has a mean size, which refers to the average longest dimension of the clusters of primary nanoparticles, that is no greater than 1000 nanometers, no greater than 500 nanometers, no greater than 200 nanometers, no greater than 100 nanometers, no greater than 75 nanometers, no greater than 50 nanometers, or no greater than 40 nanometers. In some embodiments, the layered nanoparticles are substantially non-agglomerated.

The layered particles to be included in a nanocomposite are typically commercially available in the form of a layered microparticle powder, for example and without limitation, talc, halloysite, hydrotalcite, montmorillonite, kaolin, and mica. Example layered silicate powder is available as talc (e.g., magnesium silicate) under the trade designation JETFINE (e.g., JETFINE 3cc) from Emerys Talc America (San Jose, Calif.), and as halloysite (e.g., aluminosilicate) under the trade designation DRAGONITE XR from Applied Materials, Inc. (New York, N.Y.). Example layered double hydroxide powder is available as hydrotalcite (e.g., hydrous aluminum and magnesium hydroxide with carbonate) under the trade designation PURAL MG 63 HT from Sasol Germany GmbH (Hamburg, Germany).

In certain embodiments, the nanocomposite or composite comprises from about 1 to about 70 weight percent of the layered nanoparticles, or from about 3 to about 30 weight percent, or from about 5 to about 30 weight percent, or from about 10 to about 50 weight percent, or from about 10 to about 70 weight percent, or from about 15 to about 30 weight percent, or from about 15 to about 50 weight percent, or from about 20 to about 50 weight percent, or from about 25 to about 50 weight percent, or from about 15 to about 70 weight percent, or from about 25 to about 70 weight percent, or from about 35 to about 70 weight percent, or from about 50 to about 70 weight percent of the layered nanoparticles. In an aspect, the nanocomposite consists essentially of the layered nanoparticles and a dispersant dispersed in the curable resin. In an aspect, the article consists essentially of the layered nanoparticles and a dispersant dispersed in the cured resin.

Nanoparticles, including surface-modified nanoparticles, have been compounded into curable resins to alter the properties of the resulting cured resin system. For example, U.S. Pat. No. 5,648,407 (Goetz et al.) describes, among other things, curable resins comprising colloidal microparticles in curable resin, and the use of such particle-containing resins in combination with reinforcing fibers. International Patent Publication No. WO2008/027979 (Goenner et al.) describes, among other things, resin systems comprising one or more crosslinkable resins, one or more reactive diluents, and a plurality of reactive, surface-modified nanoparticles.

Traditionally, nanoparticles have been compounded into resins using a combination of solvent exchange and solvent stripping processes. In addition to being time-consuming and requiring the use of multiple solvents, such processes often expose the curable resins to high temperatures. Such high temperatures can lead to oligomerization and other undesirable reactions during the compounding process with a resultant increase in viscosity. In addition, low-boiling-temperature components (e.g., volatile reactive diluents) may be lost during these compounding steps.

Moreover, prior to solvent stripping, silica nanoparticle dispersions typically contain only about 20% by weight nanoparticles, thus to make a concentrated (e.g., 50 wt. %) nanocomposite is difficult, particularly when employing a batch process requiring a large volume stripping unit to contain the feed, 80 vol. % of which is waste (e.g., water and solvent).

Alternatively, layered nanoparticles have been compounded into resins using layered nanoparticles that are pretreated with intercalating agents to intercalate the layered nanoparticles prior to dispersion. For instance, common intercalating agents include tertiary and quaternary ammonium salts (e.g., trimethyl octadecyl ammonium chloride, dimethyl dioctadecyl ammonium chloride, dimethyl benzyl octadecyl ammonium chloride, and tetraethyl ammonium chloride), octadecylamine, w-aminododecanoic acid, methyl cocodipolyethylene glycol, protonated alkyl amines (e.g., butyl, hexyl, octyl, dodecyl, hexadecyl, or octadecyl), 2-phenylethylamine, methyl tallow dihydroxy ethyl ammonium chloride, quaternary phosphonium bromides (e.g., tributyl hexadecyl phosphonium bromide), 1,2-dimethyl-3-n-hexadecyl imidazolium bromide, bis(aminopropyl)-terminated oligo(propylene glycol), 1-methyl-2-norstearyl-3-stearinoacid amidoethyldihydroimidazolinium methyl sulfate, hydroxyethyl dihydroimidazolinium chloride, ricinyl dihydroimidazolinium chloride, and a dimethyl isophthalate substituted with a triphenylphosphonium group.

Further, layered nanoparticles have been intercalated in situ using liquid monomers, such as monomers of thermoplastic polymers, or melt-intercalated by molten polymers. In such methods the layered nanoparticles are typically swollen with liquid monomer or molten polymer prior to curing.

The present disclosure provides alternative procedures for combining layered nanoparticles, including agglomerated layered nanoparticles, into a curable resin. These procedures do not require the use of solvents or pretreatments and may be used to compound curable resins without causing premature cure.

Layered particles have been included in resin systems as thickeners; generally, the larger the aspect ratio, the greater the increase in viscosity of the layered particle-containing resin. Such thickening effects can be observed at layered particle loadings of as little as 5 weight percent (wt. %), 3 wt. %, or even 2 wt. %. Typically, a loading of about 10 weight percent or more layered microparticles or layered nanoparticles in resin poses challenges with respect to effective dispersion of the particles within the resin. For example, high resin system viscosities (e.g., greater than about 1,000 centipoises (cP), or greater than about 5,000 cP) inhibits dispersion of layered particles into a resin system according to usual methods. Moreover, a decrease in tensile strength, impact strength, fracture toughness, and strain at break of polymer clay composites has been reported as clay content increases, believed to be due to agglomeration of clay particles at higher concentrations higher viscosity, and nanovoid formation from entrapped air bubbles during sample preparation. (See Azeez A A et al. Epoxy clay nanocomposites—processing, properties and applications: A review. Composites: Part B, volume 45, issue 1, February 2013, pp. 308-320.)

In contrast to prior systems, certain embodiments of the nanocomposites, articles, and methods of the present disclosure achieve dispersion of layered particles at high loadings (e.g., at least 4 wt. %, at least 6 wt. %, at least 8 wt. %, at least 10 wt. %, at least 12 wt. %, at least 15 wt. %, at least 20 wt. %, at least 25 wt. %, at least 30 wt. %, at least 35 wt. %, at least 40 wt. %, at least 45 wt. %, at least 50 wt. %, at least 55 wt. %, at least 60 wt. %, or at least 65 wt. %) without requiring the use of solvents to decrease the viscosity of the resin system. Similarly, embodiments of the nanocomposites, articles, and methods of the present disclosure achieve dispersion of layered nanoparticles at high loadings without requiring a pretreatment of the layered nanoparticles with surface treatment agents to improve the compatibility of the layered nanoparticles with the specific resin(s) of the resin system or to intercalate the layered nanoparticles before dispersion.

Generally, curable resin systems are used in a wide variety of applications, e.g., as a protective layer (e.g., gel coats) and as the impregnation resin in composites. Advanced structural composites, for example, are high modulus, high strength materials useful in many applications requiring high strength to weight ratios, e.g., applications in the automotive, sporting goods, and aerospace industries. Exemplary composites include for example and without limitation, a turbine blade, golf club, a baseball bat, a fishing rod, a racquet, a bicycle frame, a pressure vessel (e.g., a container having pressurized contents), an aerospace part (e.g., an exterior panel of an airplane), and a cable (e.g., a hoist cable, an underwater tether, an umbilical cable, and the like). Such composites typically comprise reinforcing fibers (e.g., carbon or glass) embedded in a cured matrix resin. Resin systems are often selected based on the desired mechanical properties of the final product including, e.g., hardness, toughness, fracture resistance, and the like. In some applications, the optical appearance of the finished product may be important such that properties like clarity and haze must be considered. In addition, process conditions may lead to preferred ranges for properties such as viscosity. Finally, the desired end use of the product often leads to additional requirements, e.g., erosion resistance or anti-blistering.

Curable resins suitable for use in the nanocomposites of the invention are those resins, e.g., thermosetting resins and radiation-curable resins, which are capable of being cured to form a glassy network polymer. Suitable resins include, e.g., epoxy resins, curable imide resins (especially maleimide resins, but also including, e.g., commercial K-3 polyimides (available from DuPont) and polyimides having a terminal reactive group such as acetylene, diacetylene, phenylethynyl, norbornene, nadimide, or benzocyclobutane), vinyl ester resins and acrylic resins (e.g., (meth)acrylic esters or amides of polyols, epoxies, and amines), bisbenzocyclobutane resins, polycyanate ester resins, and mixtures thereof. The resins can be utilized in the form of either monomers or prepolymers. Preferred curable resins include epoxy resins, maleimide resins, polycyanate ester resins, and mixtures thereof. Epoxy resins are especially preferred due to their processing characteristics, high temperature properties, and environmental resistance.

Epoxy resins are well-known in the art and comprise compounds or mixtures of compounds which contain one or more epoxy groups of the structure

The compounds can be saturated or unsaturated, aliphatic, alicylic, aromatic, or heterocyclic, or can comprise combinations thereof. Compounds which contain more than one epoxy group (i.e., polyepoxides) are preferred.

Polyepoxides which can be utilized in the nanocomposites of the invention include, e.g., both aliphatic and aromatic polyepoxides, but aromatic polyepoxides are preferred for high temperature applications. The aromatic polyepoxides are compounds containing at least one aromatic ring structure, e.g. a benzene ring, and more than one epoxy group. Preferred aromatic polyepoxides include the polyglycidyl ethers of polyhydric phenols (e.g., bisphenol A derivative resins, epoxy cresol-novolac resins, bisphenol F derivative resins, epoxy phenol-novolac resins), glycidyl esters of aromatic carboxylic acids, and glycidyl amines of aromatic amines. The most preferred aromatic polyepoxides are the polyglycidyl ethers of polyhydric phenols.

Representative examples of aliphatic polyepoxides which can be utilized in the nanocomposites of the invention include 3′,4′-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxycyclohexyloxirane, 2-(3′,4′-epoxycyclohexyl)-5,1″-spiro-3″,4″-epoxycyclohexane-1,3-dioxane, bis(3,4-epoxycyclohexylmethyl)adipate, the diglycidyl ester of linoleic dimer acid, 1,4-bis(2,3-epoxypropoxy)butane, 4-(1,2-epoxyethyl)-1,2-epoxycyclohexane, 2,2-bis(3,4-epoxycyclohexyl)propane, polyglycidyl ethers of aliphatic polyols such as glycerol or hydrogenated 4,4′-dihydroxydiphenyl-dimethylmethane, and mixtures thereof.

Representative examples of aromatic polyepoxides which can be utilized in the nanocomposites of the invention include glycidyl esters of aromatic carboxylic acids, e.g., phthalic acid diglycidyl ester, isophthalic acid diglycidyl ester, trimellitic acid triglycidyl ester, and pyromellitic acid tetraglycidyl ester, and mixtures thereof. N-glycidylaminobenzenes, e.g., N,N-diglycidylbenzeneamine, bis(N,N-diglycidyl-4-aminophenyl)me thane, 1,3-bis(N,N-diglycidylamino)benzene, and N,N-diglycidyl-4-glycidyloxybenzeneamine, and mixtures thereof; and the polyglycidyl derivatives of polyhydric phenols, e.g., 2,2-bis-[4-(2,3-epoxypropoxy)phenyl]propane, the polyglycidyl ethers of polyhydric phenols such as tetrakis(4-hydroxyphenyl)ethane, pyrocatechol, resorcinol, hydroquinone, 4,4′-dihydroxydiphenyl methane, 4,4′-dihydroxydiphenyl dimethyl methane, 4,4′-dihydroxy-3,3′-dimethyldiphenyl methane, 4,4′-dihydroxydiphenyl methyl methane, 4,4′-dihydroxydiphenyl cyclohexane, 4,4′-dihydroxy-3,3′-dimethyldiphenyl propane, 4,4′-dihydroxydiphenyl sulfone, and tris-(4-hydroxyphenyl)methane, polyglycidyl ethers of novolacs (reaction products of monohydric or polyhydric phenols with aldehydes in the presence of acid catalysts), and the derivatives described in U.S. Pat. No. 3,018,262 (Schoeder) and U.S. Pat. No. 3,298,998 (Coover et al.), the descriptions of which are incorporated herein by reference, as well as the derivatives described in the Handbook of Epoxy Resins by Lee and Neville, McGraw-Hill Book Co., New York (1967) and in Epoxy Resins, Chemistry and Technology, Second Edition, edited by C. May, Marcel Dekker, Inc., New York (1988), and mixtures thereof. A preferred class of polyglycidyl ethers of polyhydric phenols for use in the nanocomposites of the invention is the diglycidyl ethers of bisphenol that have pendant carbocyclic groups, e.g., those described in U.S. Pat. No. 3,298,998 (Coover et al.), the description of which is incorporated herein by reference. Examples of such compounds include 2,2-bis[4-(2,3-epoxypropoxy)phenyl]norcamphane and 2,2-bis[4-(2,3-epoxypropoxy)phenyl]decahydro-1,4,5,8-dimethanonaphthalene. A preferred compound is 9,9-bis[4-(2,3-epoxypropoxy)phenyl]fluorene.

Suitable epoxy resins can be prepared by, e.g., the reaction of epichlorohydrin with a polyol, as described, e.g., in U.S. Pat. No. 4,522,958 (Das et al.), the description of which is incorporated herein by reference, as well as by other methods described by Lee and Neville and by May, supra. Many epoxy resins are also commercially available.

Maleimide resins suitable for use in the nanocomposites of the invention include bismaleimides, polymaleimides, and polyaminobismaleimides. Such maleimides can be conveniently synthesized by combining maleic anhydride or substituted maleic anhydrides with di-or polyamine(s). Preferred are N,N′-bismaleimides, which can be prepared, e.g., by the methods described in U.S. Pat. No. 3,562,223 (Bargain et al.), U.S. Pat. No. 3,627,780 (Bonnard et al.), U.S. Pat. No. 3,839,358 (Bargain), and U.S. Pat. No. 4,468,497 (Beckley et al.) (the descriptions of which are incorporated herein by reference) and many of which are commercially available.

Representative examples of suitable N,N′-bismaleimides include the N,N′-bismaleimides of 1,2-ethanediamine, 1,6-hexanediamine, trimethyl-1,6-hexanediamine, 1,4-benzenediamine, 4,4′-methylenebisbenzenamine, 2-methyl-1,4-benzenediamine, 3,3′-methylenebisbenzenamine, 3,3′-sulfonylbisbenzenamine, 4,4′-sulfonylbisbenzenamine, 3,3′-oxybisbenzenamine, 4,4′-oxybisbenzenamine, 4,4′-methylenebiscyclohexanamine, 1,3-benzenedimethanamine, 1,4-benzenedimethanamine, 4,4′-cyclohexanebisbenzenamine, and mixtures thereof.

Co-reactants for use with the bismaleimides can include any of a wide variety of unsaturated organic compounds, particularly those having multiple unsaturation, either ethylenic, acetylenic, or both. Examples include acrylic acids and amides and the ester derivatives thereof, e.g., acrylic acid, methacrylic acid, acrylamide, methacrylamide, and methylmethacrylate; dicyanoethylene; tetracyanoethylene; allyl alcohol; 2,2′-diallylbisphenol A; 2,2′-dipropenylbisphenol A; diallylphthalate; triallylisocyanurate; triallylcyanurate; N-vinyl-2-pyrrolidinone; N-vinyl caprolactam; ethylene glycol dimethacrylate; diethylene glycol dimethacrylate; trimethylolpropane triacrylate; trimethylolpropane trimethacrylate; pentaerythritol tetramethacrylate; 4-allyl-2-methoxyphenol; triallyl trimellitate; divinyl benzene; dicyclopentadienyl acrylate; dicyclopentadienyloxyethyl acrylate; 1,4-butanediol divinyl ether; 1,4-dihydroxy-2-butene; styrene; .alpha.-methyl styrene; chlorostyrene; p-phenylstyrene; p-methylstyrene; t-butylstyrene; and phenyl vinyl ether. Of particular interest are resin systems employing a bismaleimide in combination with a bis(alkenylphenol). Descriptions of a typical resin system of this type are found in U.S. Pat. No. 4,100,140 (Zahir et al.), the descriptions of which are incorporated herein by reference. Particularly preferred components are 4,4′-bismaleimidodiphenylmethane and o,o′-diallyl bisphenol A.

Polycyanate ester resins suitable for use in the nanocomposites of the invention can be prepared by combining cyanogen chloride or bromide with an alcohol or phenol. The preparation of such resins and their use in polycyclotrimerization to produce polycyanurates are described in U.S. Pat. No. 4,157,360 (Chung et al.), the descriptions of which are incorporated herein by reference. Representative examples of suitable polycyanate ester resins include 1,2-dicyanatobenzene, 1,3-dicyanatobenzene, 1,4-dicyanatobenzene, 2,2′-dicyanatodiphenylmethane, 3,3′-dicyanatodiphenylmethane, 4,4′-dicyanatodiphenylmethane, and the dicyanates prepared from biphenol A, bisphenol F, and bisphenol S. Tri- and higher functionality cyanate resins are also suitable.

In some embodiments, the curable resin may be an ethylenically-unsaturated curable resin. For example, in some embodiments, an unsaturated polyester resin may be used. In some embodiments, the unsaturated polyester resin is the condensation product of one or more carboxylic acids or derivatives thereof (e.g., anhydrides and esters) with one or more alcohols (e.g., polyhydric alcohols).

In other embodiments, vinyl ester resins are used. As used herein, the term “vinyl ester” refers to the reaction product of epoxy resins with ethylenically-unsaturated monocarboxylic acids. Exemplary epoxy resins include bisphenol A digycidyl ether (e.g., EPON 828, available from Hexion Specialty Chemicals, Columbus, Ohio). Exemplary monocarboxylic acids include acrylic acid and methacrylic acid. Although such reaction products are acrylic or methacrylic esters, the term “vinyl ester” is used consistently in the gel coat industry. (See, e.g., Handbook of Thermoset Plastics (Second Edition), William Andrew Publishing, page 122 (1998).)

In still other embodiments, (meth)acrylate resins, including, e.g., urethane (meth)acrylates, polyethyleneglycol (multi)(meth)acrylates, and epoxy (multi)(meth)acrylates may be used. In other embodiments, direct milling into epoxy resins may be achieved. Epoxy resins may contain diluents such as hexanedioldiglycidyl ether.

Depending on the selection of the curable resin, in some embodiments, the resin system may also include a reactive diluent. Exemplary reactive diluents include styrene, alpha-methylstyrene, vinyl toluene, divinylbenzene, triallyl cyanurate, methyl methacrylate, diallyl phthalate, ethylene glycol dimethacrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, and other mono- and multi-functional (meth)acrylates.

In certain embodiments of the nanocomposite, the curable resin comprises an epoxy resin, a curable imide resin, a vinyl ester resin, an acrylic resin, a bisbenzocyclobutane resin, a polycyanate ester resin, or a mixture thereof. In an embodiment, the curable resin comprises an epoxy resin, a maleimide resin, a polycyanate ester resin, or a mixture thereof. In an embodiment, the curable resin comprises an epoxy resin or a mixture of epoxy resins. In an embodiment, the curable resin comprises a digycidyl ether of bisphenol A, a diglycidyl ether of bisphenol F, ethylidene bis-4,1-phenylene dicyanate, N,N′-4,4′-diphenylmethanebismaleimide, 4,4′-(1-methylethylidene)bis(2-(2-propenyl)phenol), or a mixture thereof.

Similarly, in certain embodiments of the article, the cured resin comprises an epoxy resin, a cured imide resin, a vinyl ester resin, an acrylic resin, a bisbenzocyclobutane resin, a polycyanate ester resin, or a mixture thereof. Such resins are discussed in detail above. In an embodiment, the cured resin comprises an epoxy resin, a maleimide resin, a polycyanate ester resin, or a mixture thereof. In an embodiment, the cured resin comprises an epoxy resin or a mixture of epoxy resins. In an embodiment, the cured resin comprises a digycidyl ether of bisphenol A, a diglycidyl ether of bisphenol F, ethylidene bis-4,1-phenylene dicyanate, N,N′-4,4′-diphenylmethanebismaleimide, 4,4′-(1-methylethylidene)bis(2-(2-propenyl)phenol), or a mixture thereof.

The nanocomposite or article further includes one or more dispersants. The dispersant acts to stabilize the nanoparticle in the matrix material during and after milling. Without dispersant, the nanoparticles may reaggregate, thus adversely affecting the benefit of the nanoparticle in the matrix material. Preferred dispersants according to this disclosure are free of solvent and typically referred to as dispersant that are “100% solids” or “solvent-free.” The dispersants typically have an anchoring (or binding) group that interacts with the nanoparticle and a tail (or extender) portion that is compatible with the matrix material. Additional functionality may be incorporated in the dispersant, such as reactive groups present in the tail or extender portion of the dispersant that react with the matrix material. The anchoring or binding group of the dispersant may interact with the nanoparticle through ionic bonding, acid/base interactions, hydrogen bonding, polarization interaction, and/or van der Waals interactions. There may be one anchoring group per dispersant molecule or many anchoring groups, as is the case for so-called “comb polymers.” The tail portion of the dispersant is of sufficient length to provide a steric barrier to prevent the nanoparticle from reaggregating.

Suitable dispersants include for example and without limitation, a copolymer comprising acidic groups, for instance BYK W9010. Another suitable dispersant is BYK 2152, which is a hyperbranched high molecular weight polyester with aminic groups. Each of the BYK dispersants is commercially available from BYK USA, Inc. (Wallingford, Conn.). A further suitable dispersant is a nonionic polymeric polyester copolymer, for instance ZEPHRYM PD 2246, which is commercially available from Croda, Inc. (Edison, N.J.). Another suitable dispersant is a slightly anionic polymeric polyester having part acid functionality, for instance ZEPHRYM PD 1000, which is commercially available from Croda, Inc. (Edison, N.J.). An additional suitable dispersant is an acrylic polymer salt, for example SOLPLUS D570, which is commercially available from Lubrizol Additives (Wickliffe, Ohio). Another suitable dispersant is a Jeffamine sulfonate, the sulfonic acid ligand containing JEFFAMINE M-6000 (commercially available from Huntsman Corporation, (The Woodlands, Tex.)) reacted with propane sulfone, as described in International Patent Publication No. WO 2010/080459 (Schultz et al.). Other suitable dispersants include polymeric dispersants commercially available under the trade designations SOLPLUS D510 (available from Lubrizol Additives (Wickliffe, Ohio). In many embodiments, the polymeric dispersants are added to the nanocomposite at the same time as the aggregated layered nanoparticles and curable resin. The polymeric dispersants are often added to the nanocomposite at the same time as the aggregated layered nanoparticles and curing agent. Typical high molecular weight dispersants are polymeric and have weight average molecular weights (Mw) of greater than 1000 gm/mole, or even greater than 2000 gm/mole. In certain embodiments, the dispersant is crosslinkable.

In certain embodiments, the nanocomposite or article comprises from about 0.5% to 20% by weight, inclusive, of the dispersant, or from about 0.5 to about 10% by weight, or from about 0.5 to about 5.0% by weight, or from about 0.5 to about 3.0% by weight, or from about 0.5 to about 2.0% by weight percent, or from about 0.5 to about 1.0% by weight dispersant,

Nanocomposites comprising layered nanoparticles and a dispersant dispersed in a curable resin comprise a wide viscosity range, such as of 50 to 200 Pascals·second (Pa·s), inclusive, as measured according to ASTM D2196 at 30 degrees Celsius, or up to about 6,000 Pa·s, as measured according to ASTM 2196 at 50 degrees Celsius. Advantageously, in embodiments comprising hydrotalcite layered nanoparticles and a dispersant dispersed in a curable resin, a viscosity comparable to the viscosity of nanocomposites instead containing spherical colloidal silica nanoparticles is attained. For instance, a nanocomposite comprising 20 wt. % nanoparticles, hydrotalcite layered and a dispersant, dispersed in a curable resin typically comprises a viscosity of less than 100 Pa·s, or less than 80 Pas (as measured according to ASTM D2196 at 30 degrees Celsius).

In an embodiment, the layered nanoparticles include at least one intercalating agent for preventing aggregation and/or agglomeration of layered nanoparticles (or clusters of layered nanoparticles. Suitable intercalating agents include for example and without limitation the intercalating agents disclosed above.

In an embodiment, the nanocomposite or article includes one or more catalysts for reacting silanol groups on the surface of the layered nanoparticles with the curable resin system. Suitable catalysts include for instance stannous chloride (SnCl₂) and methylethylketone peroxide.

In an embodiment, the nanocomposite or article includes one or more defoamers for acting as a defoamer and/or as an entrapped air release agent. Suitable defoamers include for instance BYK-1790 and BYK-A535, silicone-free polymeric defoamers, and BYK-A500 air release additives, commercially available from BYK USA, Inc. (Wallingford, Conn.).

Generally, “surface modified nanoparticles” comprise surface treatment agents attached to the surface of a nanoparticle. Advantageously, according to methods of the present disclosure, it is not necessary to modify the surface of layered nanoparticles in a separate step, prior to incorporating the nanoparticles into the nanocomposite. Surface treatment agents, if desired, can simply be added to the nanocomposite and mixed in with the curable resin and layered nanoparticles, treating the surfaces of the layered nanoparticles during the dispersion of the layered nanoparticles in the curable resin.

In many embodiments, a surface treatment agent is an organic species having a first functional group capable of chemically attaching (e.g., covalently or ionically bonding) or physically attaching (e.g., strong physisorptively attaching) to the surface of a nanoparticle, wherein the attached surface treatment agent alters one or more properties of the nanoparticle. In some embodiments, covalently-bonded surface treatment agents may be preferred. In some embodiments, surface treatment agents have no more than three functional groups for attaching to the core. In some embodiments, the surface treatment agents have a low molecular weight, e.g. a weight average molecular weight less than 1000 grams per mole. In some embodiments, the surface treatment agent is an organosilane (e.g., alkyl chlorosilanes, trialkoxy arylsilanes, or trialkoxy alkylsilanes) or a compound having oxirane groups. Exemplary surface treatment agents include methacryloxypropyltrimethoxysilane, phenyl trimethoxysilane, 3-(trimethoxysilyl)propyl methacrylate) polyethyleneglycol(trimethoxy)silane benzooxasilepin dimethyl ester, phenethyltrimethoxysilane, N-phenylaminopropyl trimethoxysilane, diglycidylether of bisphenol-A, glycidylmethacrylate, allylglycidylether, or combinations thereof.

In some embodiments, the surface treatment agent further includes one or more additional functional groups providing one or more additional desired properties. For example, in some embodiments, an additional functional group may be selected to provide a desired degree of compatibility between the surface modified nanoparticles and one or more of the additional constituents of the resin system, e.g., one or more of the curable resins and/or diluents. In some embodiments, an additional functional group may be selected to modify the rheology of the resin system, e.g., to increase or decrease the viscosity, or to provide non-Newtonian rheological behavior, e.g., thixotropy (shear-thinning) In an embodiment, the layered nanoparticles comprise treated surfaces, for example layered nanoparticle surfaces treated with an organosilane, a monohydric alcohol, or a polyol.

In some embodiments, the surface-modified nanoparticles are reactive; that is, at least one of the surface treatment agents used to surface modify the nanoparticles of the present disclosure may include a second functional group capable of reacting with one or more of the curable resin(s) and/or one or more reactive diluent(s) present in the nanocomposite.

In an embodiment, the nanocomposite or article includes at least one diluent, including at least one reactive diluent. Suitable diluents include, a polyfunctional glycidyl ether, styrene, mono- and multi-functional (meth)acrylates, or combinations thereof. Some exemplary suitable diluents include for example and without limitation dicyclopentenyloxyethyl methacrylate, alpha-methylstyrene, vinyl toluene, divinylbenzene, triallyl cyanurate, methyl methacrylate, diallyl phthalate, ethylene glycol dimethacrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate. Other suitable reactive diluents for epoxy resins include for example mono- and multi-functional, aliphatic and aromatic, glycidyl ethers including, e.g., some of those available under the trade name HELOXY from Hexion Specialty Chemicals, Columbus, Ohio. Exemplary reactive diluents include, e.g., polypropylene glycol diglycidyl ether, allyl glycidyl ether, trimethylol propane trigylcidyl ether, 1,4-butane diol diglycidyl ether, neopentyl glycol diglycidyl ether, n-butyl glycidyl ether, 2-ethylhexyl glycidyl ether, p-tertiary butyl phenyl glycidyl ether, phenyl glycidyl ether, and cyclohexane dimethanol diglycidyl ether.

In certain embodiments, the nanocomposite or article includes a curing agent. The term “curative” as used herein also refers to a curing agent. Typically, the curing agent comprises an amine curing agent, an anhydride curing agent, a dicyandiamide curing agent, or a combination thereof. More particularly, in an aspect, the curing agent comprises an amine curing agent. In an aspect, the curing agent comprises an anhydride curing agent. In an aspect, the curing agent comprises a dicyandiamide curing agent. In an aspect, the curing agent comprises a mixed curing agent. A suitable amine curing agent includes for instance EPIKURE 3230 (commercially available from Momentive Performance Materials Inc. (Albany, N.Y.)) and a suitable anhydride curing agent includes for example LINDRIDE 36V (commercially available from Lindau Chemicals Inc. (Columbia S.C.)).

Epoxy resins can be cured by a variety of curing agents, some of which are described (along with a method for calculating the amounts to be used) by Lee and Neville in Handbook of Epoxy Resins, McGraw-Hill, pages 36-140, New York (1967). Useful epoxy resin curing agents include polyamines such as ethylenediamine, diethylenetriamine, aminoethylethanolamine, and the like, diaminodiphenylsulfone, 9,9-bis(4-aminophenyl)fluorene, 9,9-bis(3-chloro-4-(aminophenyl)fluorene, amides such as dicyandiamide, polycarboxylic acids such as adipic acid, acid anhydrides such as phthalic anhydride and chlorendic anhydride, and polyphenols such as bisphenol A, and the like. Generally, the epoxy resin and curing agent are used in stoichiometric amounts, but the curing agent can be used in amounts ranging from about 0.1 to 1.7 times the stoichiometric amount of epoxy resin.

Thermally-activated catalytic agents, e.g., Lewis acids and bases, tertiary amines, imidazoles, complexed Lewis acids, and organometallic compounds and salts, can also be utilized in curing epoxy resins. Thermally-activated catalysts can generally be used in amounts ranging from about 0.05 to about 5 percent by weight, based on the amount of epoxy resin present in the curable resin nanocomposite.

N,N′-bismaleimide resins can be cured using diamine curing agents, such as those described in U.S. Pat. No. 3,562,223 (Bargain et al.), the description of which is incorporated herein by reference. Generally, from about 0.2 to about 0.8 moles of diamine can be used per mole of N,N′-bismaleimide. N,N′-bismaleimides can also cure by other mechanisms, e.g., co-cure with aromatic olefins (such as bis-allylphenyl ether, 4,4′-bis(o-propenylphenoxy)benzophenone, or o,o′-diallyl bisphenol A) or thermal cure via a self-polymerization mechanism.

Polycyanate resins can be cyclotrimerized by application of heat and/or by using catalysts such as zinc octoate, tin octoate, zinc stearate, tin stearate, copper acetylacetonate, and chelates of iron, cobalt, zinc, copper, manganese, and titanium with bidentate ligands such as catechol. Such catalysts can generally be used in amounts of from about 0.001 to about 10 parts by weight per 100 parts of polycyanate ester resin.

In certain embodiments, the nanocomposite or article further comprises reinforcing fibers, and optionally the reinforcing fibers are continuous. Suitable reinforcing fibers include for example and without limitation, carbon, glass, ceramic, boron, silicon carbide, polyimide, polyamide, polyethylene, or a combination thereof. In an embodiment, the reinforcing fibers comprise a unidirectional array of individual continuous fibers, woven fabric, knitted fabric, yarn, roving, braided constructions, or non-woven mat.

Advantageously, the nanocomposite is suitable for use in a prepreg, which includes any reinforcing or molding material that can be impregnated with the nanocomposite. In an embodiment, a prepreg includes the nanocomposite of any of the aspects or embodiments disclosed above. The curable nanocomposites of the invention can be used to make composite articles by a variety of conventional processes, e.g., resin transfer molding, filament winding, tow placement, resin infusion processes, compression sheet molding, or traditional prepreg processes. Prepregs can be prepared by impregnating an array of fibers (or a fabric) with the nanocomposite and then layering the impregnated tape or fabric. The resulting prepreg can then be cured by application of heat, along with the application of pressure or vacuum (or both) to remove any trapped air.

The nanocomposites can also be used to make composite parts by a resin transfer molding process, which is widely used to prepare composite parts for the aerospace and automotive industries. In this process, fibers are first shaped into a preform which is then compressed to final part shape in a metal mold. The nanocomposite can then be deposited into the mold and heat-cured.

Composites can also be prepared from the nanocomposites by a filament winding process, which is typically used to prepare cylinders or other composites having a circular or oval cross-sectional shape. In this process, a fiber tow or an array of tows is impregnated with the nanocomposite by running it through a resin bath (preferably, containing a low viscosity resin) and immediately winding the impregnated tow onto a mandrel. The resulting composite can then be heat-cured.

A pultrusion process (a continuous process used to prepare constant cross-section parts) can also be used to make composites from the curable resin sols. In such a process, a large array of continuous fibers is first wetted out in a resin bath (preferably, containing a low viscosity resin). The resulting wet array is then pulled through a heated die, where trapped air is squeezed out and the resin is cured.

In a further exemplary embodiment, a method is provided of preparing a nanoparticle-containing curable resin system. The method comprises mixing from 1 to 70 weight percent of aggregated layered nanoparticles with a curable resin, a first dispersant, and optionally a catalyst, a surface treatment agent, and/or a diluent, to form a first mixture, wherein the mixture includes less than 2% by weight solvent; milling the first mixture in a first immersion mill including milling media to form a milled resin system comprising layered nanoparticles and the dispersant dispersed in the curable resin.

Advantageously, methods according to the present application eliminate the need to employ a solvent, or a layered nanoparticle sol to effectively disperse the layered nanoparticles in a curable resin. The layered nanoparticles, moreover, need not be functionalized with a surface treatment agent prior to mixing with a curable resin. Hence, it is a benefit of certain embodiments of the method that high loadings (e.g., greater than 10 weight percent) of aggregated layered nanoparticles are dispersed in a curable resin with a dispersant, while optionally including in the nanocomposite one or more of a catalyst, a diluent, a surface treatment agent, or a curing agent. Such optional components, however, are able to be mixed into the nanocomposite simultaneously with the aggregated layered nanoparticles, curable resin, and dispersant.

Methods of the present disclosure are typically performed using an immersion mill apparatus, which combines milling and mixing to disperse a solid component into a liquid component, particularly for high viscosity systems. One suitable immersion mill apparatus is described in U.S. Pat. No. 7,175,118 (Hockmeyer). Such immersion mill apparatuses typically include a mixing tank for holding the mixture to be milled, each of 1) a high shear impeller assembly, 2) a low shear mixer blade assembly, and 3) an immersion mill, for immersion in the mixing tank, and controllers for simultaneously operating the assemblies. In operation, the mixture is directed by the low shear mixer blade assembly to the high shear impeller assembly to initiate dispersion of the solid components into the liquid components, and then to the immersion mill for milling to decrease the aggregate sizes of any aggregated solid components (e.g., aggregated layered nanoparticles) and to further disperse the solid component in the liquid component. In certain embodiments, the milling media in the immersion mill comprises zirconia particles, preferably yttrium-stabilized zirconia beads.

The aggregated layered nanoparticles typically comprise a particle size of about 5 micrometers (μm), or between about 2 μm and about 20 μm, or between about 5 μm and about 30 μm, or between about 5 μm and about 10 μm, or between about 10 μm and about 20 μm.

In embodiments of the method, the milling of the aggregated layered nanoparticles and curable resin is performed until the aggregated layered nanoparticles are dispersed to form layered nanoparticles comprising an average particle size (of the longest dimension) in the range from about 1 nanometer to about 1000 nanometers, or from about 1 nanometer to about 500 nanometers, or from about 1 nanometer to about 100 nanometers, or from about 1 nanometer to about 50 nanometers, or from about 100 nanometers to about 400 nanometers, or from about 500 nanometers to about 1000 nanometers. The layered nanoparticles typically comprise a bimodal particle size distribution or a unimodal particle size distribution.

In certain embodiments of the method, the nanoparticle-containing curable resin system comprises from about 1 to about 70 weight percent, or from about 10 to about 30 weight percent, or from about 10 to about 50 weight percent, or from about 10 to about 70 weight percent, or from about 15 to about 50 weight percent, or from about 20 to about 50 weight percent, or from about 20 to about 35 weight percent, or from about 25 to about 50 weight percent, or from about 30 to about 50 weight percent, or from about 15 to about 70 weight percent, or from about 25 to about 70 weight percent, or from about 35 to about 70 weight percent, or from about 50 to about 70 weight percent of the layered nanoparticles. In an embodiment, the milled resin system consists essentially of about 1 to about 70 weight percent of layered nanoparticles dispersed in a curable resin with a dispersant.

In certain embodiments, the method comprises including at least one additional component (e.g., additive) with the aggregated layered nanoparticles and curable resin. Such components include for example and without limitation, diluents, catalysts, surface treatment agents, curing agents, cure accelerators, defoamers, air release agents, crosslinking agents, dyes, flame retardants, pigments, impact modifiers, and flow control agents. In certain embodiments, the method further comprises including a catalyst with the aggregated layered nanoparticles and curable resin for reacting silanol groups on the surface of the layered nanoparticles with the curable resin system. In certain embodiments, the method further comprises including a diluent with the aggregated layered nanoparticles and curable resin. In certain embodiments, the method further comprises including a surface treatment agent with the aggregated layered nanoparticles and curable resin. It is an advantage of such embodiments that a catalyst, a diluent, and/or a surface treatment agent are included in a nanocomposite comprising a curable resin and aggregated layered nanoparticles, rather than requiring mixture or reaction with the aggregated layered nanoparticles prior to mixing with the curable resin. Suitable catalyst(s), diluent(s) and surface treatment agent(s) are as described in detail above.

In some embodiments, the method further comprises including fillers (e.g., reinforcing fibers, hollow glass spheres, etc.) in the milled resin system. Fillers suitable for including in the milled resin system are as described in detail above.

Exemplary Embodiments

1. A nanocomposite including layered nanoparticles and a dispersant dispersed in a curable resin, wherein the nanocomposite contains less than 2% by weight solvent.

2. The nanocomposite of embodiment 1 wherein the layered nanoparticles include a platelet shape, an acicular shape, an irregular shape, or combinations thereof.

3. The nanocomposite of embodiment 2 wherein the irregular shaped nanoparticles include clusters of primary layered particles.

4. The nanocomposite of embodiment 2 wherein the nanoparticles are hollow.

5. The nanocomposite of embodiment 1 or embodiment 2 wherein the platelet shaped nanoparticles include talc, halloysite, hydrotalcite, montmorillonite, kaolin, mica, or combinations thereof.

6. The nanocomposite of embodiment 1, embodiment 2, or embodiment 5 wherein the nanocomposite includes an intercalating agent.

7. The nanocomposite of any one of embodiments 1 through 6 wherein the dispersant includes an anchoring group and a tail portion.

8. The nanocomposite of any one of embodiments 1 through 7 wherein the dispersant includes a phosphoric acid polyester dispersant, a Jeffamine sulfonate, a hyperbranched high molecular weight polyester, or a combination thereof.

9. The nanocomposite of any one of embodiments 1 through 8 wherein the dispersant is present in amount from 0.5% to 20% by weight, inclusive, of the total weight of the nanocomposite.

10. The nanocomposite of any one of embodiments 1 through 9 wherein the dispersant is present in amount from 0.5% to 5.0% by weight, inclusive, of the total weight of the nanocomposite.

11. The nanocomposite of any one of embodiments 1 through 10 wherein the dispersant is present in amount from 0.5% to 2.0% by weight, inclusive, of the total weight of the nanocomposite.

12. The nanocomposite of any one of embodiments 1 through 11 further including a catalyst for reacting hydroxyl groups on the surface of the nanoparticles with the curable resin system.

13. The nanocomposite of embodiment 12 wherein the catalyst includes stannous chloride (SnCl₂) or methylethylketone peroxide.

14. The nanocomposite of any one of embodiments 1 through 13 further including a surface treatment agent including an organosilane, a monohydric alcohol, a polyol, or a combination thereof.

15. The nanocomposite of embodiment 14 wherein the surface treatment agent comprises phenyl trimethoxysilane, benzooxasilepin dimethyl ester, phenethyltrimethoxy silane, N-phenylaminopropyl trimethoxysilane, or a mixture thereof.

16. The nanocomposite of any one of embodiments 1 through 15 further including at least one diluent.

17. The nanocomposite of embodiment 16 wherein the at least one diluent includes a mono- or poly-functional glycidyl ether, styrene, or a combination thereof.

18. The nanocomposite of any one of embodiments 1 through 17 further including at least one additive selected from the group consisting of curing agents, cure accelerators, defoamers, air release agents, crosslinking agents, dyes, flame retardants, pigments, impact modifiers, and flow control agents.

19. The nanocomposite of any one of embodiments 1 through 18 wherein the layered nanoparticles include a bimodal particle size distribution.

20. The nanocomposite of any one of embodiments 1 through 18 wherein the layered nanoparticles include a unimodal particle size distribution.

21. The nanocomposite of any one of embodiments 1 through 20 wherein the curable resin includes an epoxy resin, a curable imide resin, a vinyl ester resin, an acrylic resin, a bisbenzocyclobutane resin, a polycyanate ester resin, or a mixture thereof.

22. The nanocomposite of any one of embodiments 1 through 21 wherein the curable resin includes an epoxy resin, a maleimide resin, a polycyanate ester resins, or a mixture thereof.

23. The nanocomposite of any one of embodiments 1 through 22 wherein the curable resin includes a digycidyl ether of bisphenol A, a diglycidyl ether of bisphenol F, ethylidene bis-4,1-phenylene dicyanate, N,N′-4,4′-diphenylmethanebismaleimide, 4,4′-(1-methylethylidene)bis(2-(2-propenyl)phenol), or a mixture thereof.

24. The nanocomposite of any one of embodiments 1 through 23 wherein the curable resin includes an epoxy resin or a mixture of epoxy resins.

25. The nanocomposite of any one of embodiments 1 through 24 wherein the layered nanoparticles include an average particle size in the range from about 1 nanometer to about 1000 nanometers.

26. The nanocomposite of any one of embodiments 1 through 25 wherein the layered nanoparticles include an average particle size in the range from about 1 nanometer to about 500 nanometers.

27. The nanocomposite of any one of embodiments 1 through 26 wherein the layered nanoparticles include an average particle size in the range from about 1 nanometer to about 100 nanometers.

28. The nanocomposite of any one of embodiments 1 through 27 wherein the nanocomposite includes from about 1 to about 70 weight percent of the layered nanoparticles.

29. The nanocomposite of any one of embodiments 1 through 28 wherein the nanocomposite includes from about 15 to about 50 weight percent of the layered nanoparticles.

30. The nanocomposite of any one of embodiments 1 through 28 wherein the nanocomposite includes from about 50 to about 70 weight percent of the layered nanoparticles.

31. The nanocomposite of any one of embodiments 1 through 30 further including a filler including at least one of reinforcing continuous fibers, reinforcing discontinuous fibers, and hollow glass bubbles.

32. The nanocomposite of embodiment 31 wherein the filler includes at least one of reinforcing continuous fibers and reinforcing discontinuous fibers.

33. The nanocomposite of embodiment 31 or embodiment 32 wherein the filler includes carbon, glass, ceramic, boron, silicon carbide, basalt, ceramic, polyimide, polyamide, polyethylene, or a combination thereof.

34. The nanocomposite of any one of embodiments 31 through 33 wherein said reinforcing fibers include a unidirectional array of individual continuous fibers, woven fabric, knitted fabric, yarn, roving, braided constructions, or non-woven mat.

35. The nanocomposite of any one of embodiments 1 through 34 wherein the nanocomposite includes less than 0.5% by weight solvent.

36. The nanocomposite of any one of embodiments 1 through 35 further including a curing agent including an amine curing agent, an anhydride curing agent, a dicyandiamide curing agent, a diaminodiphenyl sulfone curing agent, or a combination thereof.

37. The nanocomposite of embodiment 36 wherein the curing agent includes an amine curing agent.

38. The nanocomposite of embodiment 36 wherein the curing agent includes an anhydride curing agent.

39. The nanocomposite of embodiment 36 wherein the curing agent includes a dicyandiamide curing agent.

40. The nanocomposite of embodiment 1 wherein the nanocomposite consists essentially of the layered nanoparticles and the dispersant dispersed in the curable resin.

41. A prepreg including the nanocomposite of any one of embodiments 1 through 40.

42. A composite including the cured nanocomposite of any one of embodiments 1 through 30 or 35 through 40 as a matrix resin and at least one filler embedded in the matrix resin.

43. An article including the composite of embodiment 42.

44. A composite including from about 1 to 70 weight percent of layered nanoparticles, and a dispersant, dispersed in a cured resin; and a filler embedded in the cured resin. The filler includes at least one of a reinforcing continuous fiber, reinforcing discontinuous fibers, and hollow glass bubbles.

45. The composite of embodiment 44 wherein the layered nanoparticles include a platelet shape, an acicular shape, an irregular shape, or combinations thereof.

46. The composite of embodiment 45 wherein the irregular shaped nanoparticles include clusters of primary layered particles.

47. The composite of embodiment 45 wherein the nanoparticles are hollow.

48. The composite of embodiment 44 or embodiment 45 wherein the platelet shaped nanoparticles include talc, halloysite, hydrotalcite, montmorillonite, kaolin, mica, or combinations thereof.

49. The composite of embodiment 44, embodiment 45, or embodiment 48 wherein the nanocomposite includes an intercalating agent.

50. The composite of any one of embodiments 44 through 49 wherein the dispersant includes an anchoring group and a tail portion.

51. The composite of any one of embodiments 44 through 50 wherein the dispersant includes a phosphoric acid polyester dispersant, a Jeffamine sulfonate, a hyperbranched high molecular weight polyester, or a combination thereof.

52. The composite of any one of embodiments 44 through 51 wherein the dispersant is present in amount from 0.5% to 20% by weight, inclusive, of the total weight of the nanocomposite.

53. The composite of any one of embodiments 44 through 52 wherein the dispersant is present in amount from 0.5% to 5.0% by weight, inclusive, of the total weight of the nanocomposite.

54. The composite of any one of embodiments 44 through 53 wherein the dispersant is present in amount from 0.5% to 2.0% by weight, inclusive, of the total weight of the nanocomposite.

55. The composite of any one of embodiments 44 through 54 further including a catalyst.

56. The composite of embodiment 55 wherein the catalyst includes stannous chloride (SnCl₂) or methylethylketone peroxide.

57. The composite of any one of embodiments 42 through 56 further including a surface treatment agent including an organosilane, a monohydric alcohol, a polyol, or a combination thereof.

58. The composite of embodiment 57 wherein the surface treatment agent comprises phenyl trimethoxysilane, benzooxasilepin dimethyl ester, phenethyltrimethoxy silane, N-phenylaminopropyl trimethoxysilane, or a mixture thereof.

59. The composite of any one of embodiments 44 through 58 further including at least one diluent.

60. The composite of embodiment 59 wherein the at least one diluent includes a mono- or poly-functional glycidyl ether, styrene, or a combination thereof.

61. The composite of any one of embodiments 44 through 60 further including at least one additive selected from the group consisting of curing agents, cure accelerators, defoamers, air release agents, crosslinking agents, dyes, flame retardants, pigments, impact modifiers, and flow control agents.

62. The composite of any one of embodiments 44 through 61 wherein the layered nanoparticles include a bimodal particle size distribution.

63. The composite of any one of embodiments 44 through 61 wherein the layered nanoparticles include a unimodal particle size distribution.

64. The composite of any one of embodiments 44 through 63 wherein the cured resin includes an epoxy resin, a cured imide resin, a vinyl ester resin, an acrylic resin, a bisbenzocyclobutane resin, a polycyanate ester resin, or a mixture thereof.

65. The composite of any one of embodiments 44 through 64 wherein the cured resin includes an epoxy resin, a maleimide resin, a polycyanate ester resins, or a mixture thereof.

66. The composite of any one of embodiments 44 through 65 wherein the cured resin includes a digycidyl ether of bisphenol A, a diglycidyl ether of bisphenol F, ethylidene bis-4,1-phenylene dicyanate, N,N′-4,4′-diphenylmethanebismaleimide, 4,4′-(1-methylethylidene)bis(2-(2-propenyl)phenol), or a mixture thereof.

67. The composite of any one of embodiments 44 through 66 wherein the cured resin includes an epoxy resin or a mixture of epoxy resins.

68. The composite of any one of embodiments 44 through 67 wherein the layered nanoparticles include an average particle size in the range from about 1 nanometer to about 1000 nanometers.

69. The composite of any one of embodiments 44 through 68 wherein the layered nanoparticles include an average particle size in the range from about 1 nanometer to about 500 nanometers.

70. The composite of any one of embodiments 44 through 69 wherein the layered nanoparticles include an average particle size in the range from about 1 nanometer to about 100 nanometers.

71. The composite of any one of embodiments 44 through 70 wherein the composite includes from about 10 to about 50 weight percent of the layered nanoparticles.

72. The composite of any one of embodiments 44 through 71 wherein the composite includes from about 15 to about 30 weight percent of the layered nanoparticles.

73. The composite of any one of embodiments 44 through 70 wherein the composite includes from about 50 to about 70 weight percent of the layered nanoparticles.

74. The composite of any one of embodiments 44 through 73 wherein the filler includes at least one of reinforcing continuous fibers and reinforcing discontinuous fibers.

75. The composite of embodiment 74 wherein the filler includes carbon, glass, ceramic, boron, silicon carbide, basalt, ceramic, polyimide, polyamide, polyethylene, polypropylene, polyacrylnitrile, or a combination thereof.

76. The composite of embodiment 74 or embodiment 75 wherein the reinforcing continuous fibers include a unidirectional array of individual continuous fibers, woven fabric, knitted fabric, yarn, roving, braided constructions, or non-woven mat.

77. The composite of any one of embodiments 44 through 76 further including a curing agent including an amine curing agent, an anhydride curing agent, a dicyandiamide curing agent, a diaminodiphenyl sulfone curing agent, or a combination thereof.

78. The composite of embodiment 77 wherein the curing agent includes an amine curing agent.

79. The composite of embodiment 77 wherein the curing agent includes an anhydride curing agent.

80. The composite of embodiment 77 wherein the curing agent includes a dicyandiamide curing agent.

81. The composite of embodiment 77 wherein the curing agent includes a diaminodiphenyl sulfone curing agent.

82. The composite of embodiment 44 wherein the composite consists essentially of the layered nanoparticles and dispersant dispersed in the cured resin and the filler embedded in the cured resin.

83. An article including from about 1 to about 70 weight percent of layered nanoparticles, and a dispersant, dispersed in a cured resin.

84. The article of embodiment 83 wherein the layered nanoparticles include a platelet shape, an acicular shape, an irregular shape, or combinations thereof.

85. The article of embodiment 84 wherein the irregular shaped nanoparticles include clusters of primary layered particles.

86. The article of embodiment 83 or embodiment 84 wherein the nanoparticles are hollow.

87. The article of embodiment 83 or embodiment 84 wherein the platelet shaped nanoparticles include talc, halloysite, hydrotalcite, montmorillonite, kaolin, mica, or combinations thereof.

88. The article of embodiment 83, embodiment 84, or embodiment 87 wherein the nanocomposite includes an intercalating agent.

89. The article of any one of embodiments 83 through 88 wherein the dispersant includes an anchoring group and a tail portion.

90. The article of any one of embodiments 83 through 89 wherein the dispersant includes a phosphoric acid polyester dispersant, a Jeffamine sulfonate, a hyperbranched high molecular weight polyester, or a combination thereof.

91. The article of any one of embodiments 83 through 90 wherein the dispersant is present in amount from 0.5% to 20% by weight, inclusive, of the total weight of the nanocomposite.

92. The article of any one of embodiments 1 through 91 wherein the dispersant is present in amount from 0.5% to 5.0% by weight, inclusive, of the total weight of the nanocomposite.

93. The article of any one of embodiments 1 through 92 wherein the dispersant is present in amount from 0.5% to 2.0% by weight, inclusive, of the total weight of the nanocomposite.

94. The article of any one of embodiments 83 through 93 further including a catalyst.

95. The article of embodiment 94 wherein the catalyst includes stannous chloride (SnCl₂) or methylethylketone peroxide.

96. The article of any one of embodiments 83 through 95 further including a surface treatment agent including an organosilane, a monohydric alcohol, a polyol, or a combination thereof.

97. The article of embodiment 96 wherein the surface treatment agent comprises phenyl trimethoxysilane, benzooxasilepin dimethyl ester, phenethyltrimethoxy silane, N-phenylaminopropyl trimethoxysilane, or a mixture thereof.

98. The article of any one of embodiments 83 through 97 further including at least one diluent.

99. The article of embodiment 98 wherein the at least one diluent includes a mono- or poly-functional glycidyl ether, styrene, or a combination thereof.

100. The article of any one of embodiments 83 through 99 further including at least one additive selected from the group consisting of curing agents, cure accelerators, defoamers, air release agents, crosslinking agents, dyes, flame retardants, pigments, impact modifiers, and flow control agents.

101. The article of any one of embodiments 83 through 100 wherein the layered nanoparticles include a bimodal particle size distribution.

102. The article of any one of embodiments 83 through 100 wherein the layered nanoparticles include a unimodal particle size distribution.

103. The article of any one of embodiments 83 through 102 wherein the cured resin includes an epoxy resin, a cured imide resin, a vinyl ester resin, an acrylic resin, a bisbenzocyclobutane resin, a polycyanate ester resin, or a mixture thereof.

104. The article of any one of embodiments 83 through 103 wherein the cured resin includes an epoxy resin, a maleimide resin, a polycyanate ester resins, or a mixture thereof.

105. The article of any one of embodiments 83 through 104 wherein the cured resin includes a digycidyl ether of bisphenol A, a diglycidyl ether of bisphenol F, ethylidene bis-4,1-phenylene dicyanate, N,N′-4,4′-diphenylmethanebismaleimide, 4,4′-(1-methylethylidene)bis(2-(2-propenyl)phenol), or a mixture thereof.

106. The article of any one of embodiments 83 through 105 wherein the cured resin includes an epoxy resin or a mixture of epoxy resins.

107. The article of any one of embodiments 83 through 106 wherein the layered nanoparticles include an average particle size in the range from about 1 nanometer to about 1000 nanometers.

108. The article of any one of embodiments 83 through 107 wherein the layered nanoparticles include an average particle size in the range from about 1 nanometer to about 500 nanometers.

109. The article of any one of embodiments 83 through 108 wherein the layered nanoparticles include an average particle size in the range from about 1 nanometer to about 100 nanometers.

110. The article of any one of embodiments 83 through 109 wherein the article includes from about 15 to about 50 weight percent of the layered nanoparticles.

111. The article of any one of embodiments 83 through 109 wherein the article includes from about 1 to about 5 weight percent of the layered nanoparticles.

112. The article of any one of embodiments 83 through 109 wherein the article includes from about 25 to about 70 weight percent of the layered nanoparticles.

113. The article of any one of embodiments 83 through 112 further including a filler embedded in the cured resin, wherein the filler includes at least one of reinforcing continuous fibers, reinforcing discontinuous fibers, and hollow glass bubbles.

114. The article of embodiment 113 wherein the filler includes at least one of reinforcing continuous fibers and reinforcing discontinuous fibers.

115. The article of embodiment 113 or embodiment 114 wherein the filler includes carbon, glass, ceramic, boron, silicon carbide, basalt, ceramic polyimide, polyamide, polyethylene, polypropylene, polyacrylnitrile, or a combination thereof.

116. The article of embodiment 113 through 115 wherein the reinforcing continuous fibers include a unidirectional array of individual continuous fibers, woven fabric, knitted fabric, yarn, roving, braided constructions, or non-woven mat.

117. The article of any one of embodiments 83 through 116 further including a curing agent including an amine curing agent, an anhydride curing agent, a dicyandiamide curing agent, a diaminodiphenyl sulfone, or a combination thereof.

118. The article of embodiment 117 wherein the curing agent includes an amine curing agent.

119. The article of embodiment 117 wherein the curing agent includes an anhydride curing agent.

120. The article of embodiment 117 wherein the curing agent includes a dicyandiamide curing agent.

121. The article of embodiment 117 wherein the curing agent includes a diaminodiphenyl sulfone curing agent.

122. The article of any one of embodiments 83 through 121 wherein the article includes a turbine blade, a pressure vessel, an aerospace part, a cable, or sporting goods equipment.

123. The article of embodiment 122 wherein the article includes a golf club, a baseball bat, a fishing rod, a racquet, or a bicycle frame.

124. The article of embodiment 122, wherein the article includes a pressure vessel.

125. The article of embodiment 83 wherein the article consists essentially of about 1 to about 70 weight percent of layered nanoparticles, and dispersant, dispersed in a cured resin.

126. A method of preparing a nanoparticle-containing curable resin system including mixing from 1 to 70 weight percent of aggregated layered nanoparticles with a curable resin, a dispersant, and optionally a catalyst, a surface treatment agent, and/or a diluent, to form a mixture, wherein the mixture includes less than 2% by weight solvent; and milling the mixture in a first immersion mill including milling media to form a milled resin system comprising layered nanoparticles and dispersant dispersed in the curable resin.

127. The method of embodiment 126 wherein the aggregated nanoparticles include an average size in the range from about 2 micrometers (μm) to about 20 μm.

128. The method of embodiment 126 or embodiment 127 wherein the layered nanoparticles include a platelet shape, an acicular shape, an irregular shape, or combinations thereof.

129. The method of embodiment 126 wherein the irregular shaped nanoparticles include clusters of primary layered particles.

130. The method of embodiment 128 wherein the nanoparticles are hollow.

131. The method of any one of embodiments 126 through 128 wherein the platelet shaped nanoparticles include talc, halloysite, hydrotalcite, montmorillonite, kaolin, mica, or combinations thereof.

132. The method of any one of embodiments 126 through 127 or embodiment 130 wherein the nanocomposite includes an intercalating agent.

133. The method of any one of embodiments 126 through 132 wherein the dispersant includes an anchoring group and a tail portion.

134. The method of any one of embodiments 126 through 133 wherein the dispersant includes a phosphoric acid polyester dispersant, a Jeffamine sulfonate, a hyperbranched high molecular weight polyester, or a combination thereof.

135. The method of any one of embodiments 126 through 134 wherein the dispersant is present in amount from 0.5% to 20% by weight, inclusive, of the total weight of the nanocomposite.

136. The method of any one of embodiments 126 through 135 wherein the dispersant is present in amount from 0.5% to 5.0% by weight, inclusive, of the total weight of the nanocomposite.

137. The method of any one of embodiments 126 through 136 wherein the dispersant is present in amount from 0.5% to 2.0% by weight, inclusive, of the total weight of the nanocomposite.

138. The method of any one of embodiments 126 through 137 wherein the milling media includes zirconia particles.

139. The method of any one of embodiments 126 through 138 wherein the milling media includes yttrium-stabilized zirconia beads.

140. The method of any one of embodiments 126 through 139 wherein the milling is performed until the aggregated nanoparticles are dispersed to form layered nanoparticles including an average particle size in the range from about 1 nanometer to about 1000 nanometers.

141. The method of any one of embodiments 126 through 140 wherein the layered nanoparticles include an average particle size in the range from about 1 nanometer to about 500 nanometers.

142. The method of any one of embodiments 126 through 141 wherein the layered nanoparticles include an average particle size in the range from about 1 nanometer to about 100 nanometers.

143. The method of any one of embodiments 126 through 142 further comprising including a catalyst in the mixture for reacting hydroxyl groups on the surface of the nanoparticles with the curable resin system.

144. The method of embodiment 143 wherein the catalyst includes stannous chloride (SnCl₂) or methylethylketone peroxide.

145. The method of any one of embodiments 126 through 144 further including a surface treatment agent including an organosilane, a monohydric alcohol, a polyol, or a combination thereof.

146. The method of embodiment 145 wherein the surface treatment agent includes surfaces treated with phenyl trimethoxysilane, benzooxasilepin dimethyl ester, phenethyltrimethoxy silane, N-phenylaminopropyl trimethoxysilane, or a mixture thereof.

147. The method of any one of embodiments 126 through 146 further comprising including at least one diluent in the mixture.

148. The method of embodiment 147 wherein the at least one diluent includes a mono- or poly-functional glycidyl ether, styrene, or a combination thereof.

149. The method of any one of embodiments 126 through 148 further including at least one additive selected from the group consisting of curing agents, cure accelerators, defoamers, air release agents, catalysts, crosslinking agents, dyes, flame retardants, pigments, impact modifiers, and flow control agents.

150. The method of any one of embodiments 126 through 149 wherein the layered nanoparticles include a bimodal particle size distribution.

151. The method of any one of embodiments 126 through 149 wherein the layered nanoparticles include a unimodal particle size distribution.

152. The method of any one of embodiments 126 through 151 wherein the curable resin includes an epoxy resin, a curable imide resin, a vinyl ester resin, an acrylic resin, a bisbenzocyclobutane resin, a polycyanate ester resin, or a mixture thereof.

153. The method of any one of embodiments 126 through 152 wherein the curable resin includes an epoxy resin, a maleimide resin, a polycyanate ester resins, or a mixture thereof.

154. The method of any one of embodiments 126 through 153 wherein the curable resin includes a digycidyl ether of bisphenol A, a diglycidyl ether of bisphenol F, ethylidene bis-4,1-phenylene dicyanate, N,N′-4,4′-diphenylmethanebismaleimide, 4,4′-(1-methylethylidene)bis(2-(2-propenyl)phenol), or a mixture thereof.

155. The method of any one of embodiments 126 through 154 wherein the curable resin includes an epoxy resin or a mixture of epoxy resins.

156. The method of any one of embodiments 126 through 155 wherein the milled resin system includes from about 15 to about 50 weight percent of the layered nanoparticles.

157. The method of any one of embodiments 126 through 155 wherein the milled resin system includes from about 10 to about 30 weight percent of the layered nanoparticles.

158. The method of any one of embodiments 126 through 155 wherein the milled resin system includes from about 20 to about 70 weight percent of the layered nanoparticles.

159. The method of any one of embodiments 126 through 158 further comprising including a filler in the milled resin system including at least one of reinforcing continuous fibers, reinforcing discontinuous fibers, and hollow glass bubbles.

160. The method of embodiment 159 wherein the filler includes at least one of reinforcing continuous fibers and reinforcing discontinuous fibers.

161. The method of embodiment 159 or embodiment 160 wherein the filler includes carbon, glass, ceramic, boron, silicon carbide, basalt, ceramic, polyimide, polyamide, polyethylene, polypropylene, polyacrylnitrile, or a combination thereof.

162. The method of embodiment 159 or embodiment 160 wherein the reinforcing continuous fibers include a unidirectional array of individual continuous fibers, woven fabric, knitted fabric, yarn, roving, braided constructions, or non-woven mat.

163. The method of any one of embodiments 126 through 162 further comprising including a curing agent in the mixture, the curing agent including an amine curing agent, an anhydride curing agent, a dicyandiamide curing agent, a diaminodiphenyl sulfone curing agent, or a combination thereof.

164. The method of embodiment 163 wherein the curing agent includes an amine curing agent.

165. The method of embodiment 163 wherein the curing agent includes an anhydride curing agent.

166. The method of embodiment 163 wherein the curing agent includes a dicyandiamide curing agent.

167. The method of embodiment 163 wherein the curing agent includes a diaminodiphenyl sulfone curing agent.

168. The method of embodiment 126 wherein the milled resin system consists essentially of about 1 to about 70 weight percent of layered nanoparticles, and a dispersant dispersed in a curable resin.

EXAMPLES

These Examples are merely for illustrative purposes and are not meant to be overly limiting on the scope of the appended claims. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the present disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Summary of Materials

Unless otherwise noted, all parts, percentages, ratios, etc. in the Examples and the rest of the specification are by weight. Table 1 provides a description or role, and a source, for materials used in the Examples below:

TABLE 1 Material Description or Role Source JETFINE 3cc Magnesium silicate nanoparticles Emerys Talc America, San (platelet shaped layered silicate) Jose, CA DRAGONITE XR Halloysite nanoparticles (needle Applied Materials, Inc., New shaped layered silicate) York, NY PURAL MG 63 HT Hydrotalcite nanoparticles (needle Sasol Germany GmbH, shaped layered double hydroxide) Hamburg Germany NALCO 2329 Silica nanoparticles (spherical Nalco Chemical Company, shaped) Oak Brook, IL NALCO 2327 Silica nanoparticles (spherical Nalco Chemical Company shaped) EPON 826 Liquid epoxy resin Momentive Performance Materials Inc., Albany, NY DER 332 Liquid epoxy resin Dow Chemical Company, Midland, MI BYK W9010 Dispersant - copolymer with acidic BYK USA, Inc., groups Wallingford, CT SOLPLUS D510 Dispersant - polymeric Lubrizol Additives, Wickliffe, OH Phenyl Surface treatment Momentive Performance trimethoxysilane Materials Inc. EPIKURE 3230 Amine curing agent Momentive Performance Materials Inc. 1-methoxy-2-propanol Solvent Univar USA Inc., Kirkland, WA Methylethylketone Solvent Avantor Performance Materials, Inc., Center Valley, PA Deionized water Solvent —

Particle Size Test Method

Particle size of the layered particles was measured by laser diffraction using a Horiba LA-950 (Horiba, Kyoto, Japan). The optical model used a refractive index of 1.46 for the layered particles and 1.38 for methylethylketone (MEK). The second differential method was used for smoothing based on 150 iterations. The dispersion was diluted to approximately 1 weight percent solids with MEK. The diluted sample was then added to the measurement cell which was filled with MEK until the transmittance was between the recommended levels of 85-95%. The particle size was reported as a mean (i.e., average diameter) and as a D90. D90 is defined as the diameter at which 90% of the particles have a diameter below the value.

Viscosity Test Method

Viscosity was measured according to ASTM D 2196. Measurements were performed using an AR2000 viscometer (TA Instruments, New Castle, Del.).

Glass Transition Temperature Test Method

Glass transition temperature (T_(g)) was measured according to ASTM D 7028, using a Q800 dynamic mechanical analyzer (DMA) (TA Instruments, New Castle, Del.).

Tensile Properties Test Method

Storage modulus (E′) was measured according to ASTM D 638, using a Q800 dynamic mechanical analyzer (DMA) (TA Instruments, New Castle, Del.).

Immersion Mill Method

Example layered nanocomposites were prepared using the following solvent-free milling method. A premix was prepared with the components of the layered nanocomposite. Epoxy (EPON 826 or DER 332) was preheated to 90° C. to decrease its viscosity for ease of handling. The preheated epoxy resin was transferred to a stainless steel jacketed kettle. To the kettle may be added a dispersant (W9010). 1:3 ethylene glycol:water mixture was circulated through the jacket of the kettle to control composition temperature during preparation of the premix as well as during milling. The temperature of the glycol:water mixture, and in turn, the composition was regulated by a circulator (PHOENIX II, Thermo Fisher Scientific, Newington, N.H.). The kettle containing the liquid components was secured to the frame of a disperser equipped with a 90 millimeter f-blade (DISPERMAT, CN-10, BYK-Gardner, Columbia, Md.). After activation of the f-blade and mixing of the liquid components, the dry particles were gradually added to the kettle as described in the examples.

Milling was performed using a Micro Mill immersion mill (Hockmeyer Equipment Corporation, Elizabeth City, N.C.). The immersion mill was operated with a 0.1 millimeter wire wedge screen filled with approximately 40 milliliters (65 grams) 0.5-0.7 mm yttrium-stabilized zirconia milling media (Zirmil, Saint-Gobain, Le Pontet Cedex, France). Enclosed in the media field were 8 pegs to agitate the media. A turbo prop at the bottom exterior of the screen provided the driving force for material to circulate through the media field. No auger was used when milling. The kettle containing the premix was then transferred from the disperser station to the milling station and milling initiated. The mill was operated at 4,000 revolutions per minute (rpm). Milling resulted in size reduction of the layered particles from a few micrometers to submicron size, as well as simultaneous surface modification of the particle surface, and compounding of the layered nanoparticles into the epoxy. Milling was continued until no further significant reduction in particle size was measured.

Comparative Example 1: Resin without Nanoparticles

The resin of Comparative Example 1 was pure epoxy (EPON 826).

Comparative Example 2: Nanocomposite with Spherical Nanoparticles

The silica nanocomposite of Comparative Example 2 was prepared using a mixture of surface treated colloidal silicas (NALCO 2329 and NALCO 2327). The surface treatment process of Comparative Example 2 was similar to the methods described in Examples 1 and 9-13 of International Patent Application Publication No. WO 2009/120846 (Tiefenbruck et al.). Phenyl trimethoxysilane (TMPS) was used as the surface treatment agent. Upon completion of the surface treatment process, epoxy (EPON 826) was compounded into the dispersion. The dispersion was then fed through a wiped film evaporator to remove the water and solvent from the dispersion, according to methods described in International Patent Application Publication No. WO 2011/159521 (Thunhorst et al.). The completion of the stripping process yielded a nanocomposite of silane covalently bonded to the silica in epoxy. The silica nanocomposite was diluted with epoxy (EPON 826) using a speedmixer (Model ARV-3 Vacuum Mixer, Thinky USA, Inc., Laguna Hills, Calif.) to achieve the final composition of Table 2.

Example 1: Nanocomposite with Layered Nanoparticles

The nanocomposite of Example 1 was prepared using layered double hydroxide nanoparticles (PURAL MG 63 HT) and epoxy resin (EPON 826). A dispersant (BYK W9010) was used to treat the particle surface. The dispersant was chosen to serve two purposes: 1) to reduce the tendency for the particle to reaggregate once milled to smaller sizes; and 2) to chemically modify the particle surface to make it more compatible with the matrix material (e.g. epoxy resin). The Immersion Mill Method was used to prepare the Examples. The composition, milling conditions, and viscosity are given in Table 2 below.

Example 2: Nanocomposite with Layered Nanoparticles

The nanocomposite of Example 2 was prepared as Example 1 except that layered silicate nanoparticles (DRAGONITE XR) were used. The layered silicate nanoparticles are needle-like and hollow. The composition, milling conditions, and viscosity are given in Table 2 below.

Example 3: Nanocomposite with Layered Nanoparticles

The nanocomposite of Example 3 was prepared as Example 1 except the layered silicate talc (JETFINE 3cc) was used, which is a platelet nanoparticle. SOLPLUS D510 was used as the dispersant. The composition, milling conditions, and viscosity are given in Table 2 below.

Example 4: Nanocomposite with High Loading of Layered Nanoparticles

The nanocomposite of Example 4 was prepared as Example 1 except that a higher loading of the layered double hydroxide nanoparticle (PURAL MG 63HT) was used as well as a different epoxy (DER 332). The composition, milling conditions, and viscosity are given in Table 2 below.

TABLE 2 Composition, milling conditions, and characterization of control and nanocomposites Control Solvent-based Solvent-free Example CE 1 CE 2 EX 1 EX 2 EX 3 EX 4 Particle n/a¹ NALCO PURAL DRAGONITE JETFINE PURAL Particle Shape n/a spherical platelet hollow needle platelet platelet Surface Agent n/a TMPS W9010 W9010 D510 W9010 Nanoparticle — 20.0 20.0 20.0 20.0 48.3 (wt %) Epoxy (wt %) 100.0 79.3 78.0 78.0 78.0 43.4 Surface Agent — 0.7 2.0 2.0 2.0 8.3 (wt %) Mill Time n/a n/a 5:00 5:00 15:00 6:00 (hr:min) Mill Temperature n/a n/a 95 92 112 96 (° C.) Mean Particle n/a NM² 175 396 238 241 Size (nm) D90 Particle Size n/a NM 251 1,398 516 280 (nm) Peak 1 n/a NM 97.0 84.0 85.2 97.0 Distribution (%) Viscosity @ 30 90 69 187 5,924 153 30° C. (Pa-s) (50° C.) ¹n/a: not applicable. ²NM: not measured

Comparative Example 1a: Cured Resin without Nanoparticles

Comparative Example 1a was prepared by mixing Comparative Example 1 with an amine curative (EPIKURE 3230) according to Table 3 using a speedmixer (Model ARV-3 Vacuum Mixer, Thinky USA, Inc., Laguna Hills, Calif.). The mixture was transferred to a mold and then placed in an oven. The example was cured for 2 hours at 80° C. followed by a post cure for 2 hours at 125° C.

Comparative Example 2a: Cured Silica Nanocomposite with Spherical Nanoparticles

Comparative Example 2a was prepared as Comparative Example 1a except the nanocomposite of Comparative Example 2 was used as the uncured resin.

Examples 1a-3a: Cured Nanocomposites with Layered Nanoparticles

Examples 1a-3a were prepared as Comparative Example 1a except the layered nanocomposites of Examples 1-3 were used as the uncured resin.

TABLE 3 Composition and characterization of cured control and nanocomposites Control Solvent-based Solvent-free Example CE 1a CE 2a EX 1a EX 2a EX 3a Particle n/a¹ NALCO PURAL DRAGONITE JETFINE Particle Shape n/an/a spherical platelet hollow needle platelet Surface Agent TMPS W9010 W9010 D510 Epoxy Nanocomposite (wt %) — 79.4 (CE 2) 79.1 (EX 1) 79.1 (EX 2) 79.1 (EX 3) Epoxy (EPON 826) (wt %) 56.4 — — — — Curative (EPIKURE 3230) 24.8 20.6 20.9 20.9 20.9 (wt %) E′_(glass) (Mpa) 1,256 1,447 1,521 1,381 1,691 Tg (° C.) 92.9 93.5 102.7 95.1 88.5 E′_(rubber) (Mpa) 14.64 18.73 24.44 24.84 31.18 ¹n/a: not applicable

FIG. 1 shows two of the three nanocomposites with layered nanoparticles exhibit higher viscosity than the nanocomposite with spherical nanoparticles. FIG. 2 shows the nanocomposites prepared with the layered nanoparticles exhibit higher glassy and rubber modulus relative to the unfilled resin. In FIG. 2, each of the white bars corresponds to the glassy modulus, whereas each of the patterned bars corresponds to the rubber modulus. Relative to the nanocomposite with spherical nanoparticles, the nanocomposites with the layered nanoparticles exhibit similar glassy modulus and higher rubber modulus.

FIGS. 3A and 3B provide scanning electron microscope (SEM) images of Example 1a at two different magnifications. The images show that hydrotalcite (layered double hydroxide) nanoparticles (PURAL MG 63 HT) have nonspherical shape with a broad particle size distribution, and good dispersion quality in the nanocomposite is shown. FIGS. 4A and 4B provide SEM images of Example 2a, show that the halloysite (layered silicate) nanoparticles (DRAGONITE XR) have needle shapes with a broad particle size distribution, and good dispersion quality in the nanocomposite is shown. FIGS. 5A and 5B provide SEM images of Example 3a, show that the talc (layered silicate) nanoparticles (JETFINE 3cc) have nonspherical shape with a very broad particle size distribution, and good dispersion quality in the nanocomposite is shown. The images of 3B, 4B, and 5B each show dispersions containing a combination of agglomerated layered nanoparticles, intercalated layered nanoparticles, and exfoliated layered nanoparticles.

Example 5 (Prophetic Example): Pressure Vessel Containing Solvent-Free Nanocomposite with Layered Nanoparticles

Example 5 is prepared by forming a nanocomposite with layered nanoparticles according to the formulation and method of Example 1. A pressure vessel is prepared by winding carbon fiber (e.g., TORAY T700SC-12000-50C, Lot #A2106M2, Toray Carbon Fibers America, Inc., Decatur, Ala.) saturated in the nanocomposite, according to the coating process described in U.S. application Ser. No. 13/154,615 (Thunhorst et al.). The wound vessel is then cured according to the conditions described in U.S. application Ser. No. 13/154,615 (Thunhorst et al.) to form the pressure vessel.

While the specification has described in detail certain exemplary embodiments, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing, may readily conceive of alterations to, variations of, and equivalents to these embodiments. Furthermore, all publications and patents referenced herein are incorporated by reference in their entirety to the same extent as if each individual publication or patent was specifically and individually indicated to be incorporated by reference. Various exemplary embodiments have been described. These and other embodiments are within the scope of the following claims. 

What is claimed is:
 1. A method of preparing a nanoparticle-containing curable resin system comprising: mixing from 10 to 70 weight percent of aggregated layered nanoparticles with a curable resin, a first dispersant, and optionally a catalyst, a surface treatment agent, and/or a diluent, to form a first mixture, wherein the mixture comprises less than 2% by weight solvent; and milling the first mixture in a first immersion mill comprising milling media to form a milled resin system comprising layered nanoparticles and the first dispersant dispersed in the curable resin.
 2. The method of claim 1 wherein the layered nanoparticles include a platelet shape, an acicular shape, an irregular shape, or combinations thereof.
 3. The method of claim 1 wherein the platelet shaped nanoparticles include talc, halloysite, hydrotalcite, montmorillonite, kaolin, mica, or combinations thereof.
 4. The method of claim 1, wherein the aggregated nanoparticles include an average size in the range from about 2 micrometers (μm) to about 20 μm.
 5. The method of claim 1, wherein the milling media comprises zirconia particles.
 6. The method of claim 1, wherein the milling is performed until the aggregated nanoparticles are dispersed to form layered nanoparticles including an average particle size in the range from about 1 nanometer to about 1000 nanometers.
 7. The method of claim 6, wherein the layered nanoparticles include an average particle size in the range from about 1 nanometer to about 500 nanometers.
 8. The method of claim 1, wherein the optional catalyst is present in the mixture for reacting hydroxyl groups on the surface of the nanoparticles with the curable resin system.
 9. The method of claim 1, wherein the optional surface treatment agent is present, wherein the surface treatment agent includes an organosilane, a monohydric alcohol, a polyol, or a combination thereof.
 10. The method of claim 1, wherein the optional diluent is present, wherein the at least one diluent comprises a mono- or poly-functional glycidyl ether, styrene, or a combination thereof.
 11. The method of claim 1, wherein the curable resin comprises an epoxy resin, a curable imide resin, a vinyl ester resin, an acrylic resin, a bisbenzocyclobutane resin, a polycyanate ester resin, or a mixture thereof.
 12. The method of claim 1, wherein the milled resin system comprises from about 15 to about 50 weight percent of the layered nanoparticles.
 13. The method of claim 1, wherein the milled resin system comprises from about 20 to about 70 weight percent of the layered nanoparticles.
 14. The method of claim 1, further comprising including a filler in the milled resin system comprising at least one of reinforcing continuous fibers, reinforcing discontinuous fibers, and hollow glass bubbles.
 15. The method of claim 1, further comprising including a curing agent in the mixture, the curing agent comprising an amine curing agent, an anhydride curing agent, a dicyandiamide curing agent, a diaminodiphenyl sulfone curing agent, or a combination thereof. 